1. Field of the Invention
The present invention relates generally to an apparatus and a method for managing an access mode of a Node B (NB) in a wireless communication system. More particularly, the present invention relates to an apparatus and a method for determining and changing an access mode of an NB, depending on different factors in a wireless communication system.
2. Description of the Related Art
In a conventional cellular communication system, an NB, which is connected to a mobile communication core network, provides communication services to User Equipments (UEs) that located within a cell area of the NB.
When an amount of communication in a cell area of an NB is expected to increase temporarily, for example, during a large gathering such as a party or concert, a load of the cell is also expected to increase temporarily, which may affect the quality of the communication services provided by the NB. When this occurs, the load of the cell may be distributed by temporarily adding a mobile NB, e.g., an NB mounted on a vehicle, to the area where the amount of communication is expected to be large.
Additionally, in a conventional cellular communication system, a channel state often deteriorates due to a geographical condition inside a cell, an increased distance between a UE and an NB, or movement of a UE. For example, a shadowing area may be formed inside a building, such as an office or a house, which is located inside a coverage area of an NB. If a UE is located in the shadowing area, an NB may not be able perform sufficient communication because a channel state associated with the UE is poor.
In order to improve communication in areas with poor channel conditions, a femto-cell service may be utilized. A femto cell is a small cell area formed by a compact NB that is commonly installed inside an office or a house and that accesses a mobile communication core network via a broadband network. The compact NB is a low power NB, which is often installed by a user, not the service provider and the compact NB may also be referred to as a micro NB, a self configurable NB, an indoor NB, a home NB, or a femto NB. In the following description, the compact NB is referred to as a femto NB.
There are three access modes of a femto NB that are currently under discussion in the current 3rd Generation Partnership Project Long Term Evolution (3GPP LTE), which are defined as follows.
1. Open Access Mode: a mode that grants access to all users that are not registered in an NB.
2. Closed Access Mode: a mode that grants access only to users that are registered in an NB.
3. Hybrid Access Mode: a mode that that grants access to a user that is registered in an NB, and also grants an access to users that are not registered in the NB.
The above-defined various access modes of the femto NB may also be applied to a mobile NB and a general macro NB.
Currently, when an NB is installed, e.g., a femto NB, a mobile NB, or a general macro NB, an NB access mode is permanently set. Accordingly, in an environment where neighbor NBs use the same frequency, when a UE that receives a service from an NB that utilizes an open access mode enters a coverage of an NB that utilizes a closed access mode, a serious interference factor is generated between the neighbor NBs that use the different access modes, which deteriorates communication quality.